1. Field of the Invention
The present invention relates to a method of detecting heavy metal in a semiconductor substrate, and more particularly, to a technique used for a method of detecting heavy metal in a thin semiconductor chip or a silicon wafer.
Priority is claimed on Japanese Patent Application No. 2008-105782, filed on Apr. 15, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
With the development of mobile phones, small and light electronic components are required to be mounted inside the devices. Accordingly, in order to reduce the thickness of a semiconductor package, a thinning process is performed to make the thickness of a semiconductor chip to be as small as possible. In the thinning process, a gettering sink for gettering heavy metal when heavy metal contamination occurs is thinned by the thinning process. Therefore, a gettering capability is significantly degraded, and the proportion of devices with good quality is decreased.
In the related art, in order to avoid heavy metal contamination in the vicinity of a device active layer, the following methods have been used: an IG (intrinsic gettering) method of forming an oxygen precipitate on a silicon substrate; and an EG (extrinsic gettering) method of forming a gettering site such as backside damage on the rear surface of a silicon substrate.
A technique related to the IG method is disclosed in JP-A-6-338507 and JP-A-2002-353434, and an example of the EG method described in the paragraph [0005] is disclosed in JP-T-2006-313922. In addition, an Hg-CV method is disclosed in JP-A-6-140478 and JP-A-2002-516486.
For example, heavy metal is incorporated into the thin semiconductor substrate (silicon wafer or semiconductor chip) as impurities by the following two causes: first, metal contamination during a process of manufacturing a silicon substrate including single crystal pulling, slicing, chamfering, and treatments such as polishing, grinding, etching, and epitaxial layer forming; and second, heavy metal contamination during a process of manufacturing a device element, that is, a device process including a device manufacturing process of forming a circuit on the silicon substrate and the subsequent thinning process by grinding and the like. In addition, the process of manufacturing a silicon substrate or a device requires heat treatment performed at high temperature for a long time. Therefore, there is a concern that the metal contamination of a silicon substrate will increase during the heat treatment or between processes.